update c# class examples

tutorials/scripting/c_sharp/c_sharp_basics.rst

@@ -204,9 +204,8 @@ Here's a blank C# script with some comments to demonstrate how it works.
 .. code-block:: csharp
 
     using Godot;
-    using System;
 
-    public class YourCustomClass : Node
+    public partial class YourCustomClass : Node
     {
         // Member variables here, example:
         private int a = 2;
@@ -302,7 +301,6 @@ a single code location:
 .. code-block:: csharp
 
     using Godot;
-    using System;
 
     public class YourCustomClass : Node3D
     {

tutorials/scripting/c_sharp/c_sharp_differences.rst

@@ -100,7 +100,7 @@ Example:
 
     using Godot;
 
-    public class MyNode : Node
+    public partial class MyNode : Node
     {
         [Export]
         private NodePath _nodePath;

tutorials/scripting/c_sharp/c_sharp_exports.rst

@@ -13,7 +13,9 @@ Exporting is done by using the ``[Export]`` attribute.
 
 .. code-block:: csharp
 
-    public class ExportExample : Node3D
+    using Godot;
+
+    public partial class ExportExample : Node3D
     {
         [Export]
         private int Number = 5;

tutorials/scripting/c_sharp/c_sharp_features.rst

@@ -153,7 +153,9 @@ Consequently, any ``Node`` or ``Reference`` will be compatible automatically, bu
 
 .. code-block:: csharp
 
-    public class DataObject : Godot.Object
+    using Godot;
+
+    public partial class DataObject : Godot.Object
     {
         public string Field1 { get; set; }
         public string Field2 { get; set; }